Shocking video of Oakland violence: No limits for police?

Oakland police officer deliberately firing a tear-gas canister at a group of protesters

A video has been posted online of an Oakland police officer deliberately throwing a tear-gas grenade at a group of protesters as they tried to help a demonstrator critically injured by a projectile that struck him in the head amid scenes of chaos.

Police Chief Howard Jordan says an internal review board and local prosecutors have been asked to investigate whether officers used excessive force on October 25, when police fired tear gas at protesters trying to re-establish a camp that was disbanded a day earlier.

On Wednesday, city officials in Oakland, CA, allowed Occupy Wall Street protesters back into a plaza which police had earlier raided to clear a 15-day-old encampment. However, they prohibited people from spending the night at the camp.

Hundreds of anti-Wall Street protesters in Oakland filed out of the plaza late on Wednesday night and began marching down nearby streets.

Police erected wooden barricades to channel the march but protesters circumvented their efforts by diverting their march down another street.

Oakland officials say they support the protesters' goals, but had no choice but to act when a small number of them threw rocks, paint and bottles at the police.